I feel like the Loki and Yamato comparisons are alittle disingenuous. Luffy never really had an interest in Yamato as a candidate, outside of acknowledging they weren't a threat upon first meeting. Even after finding out about their connections to Ace didn't change things. Luffy offered a spot out of a token of gratitude , instead of desire like he did with Loki. That's important. With that said.
Yamato herself had an interest in joining the crew. Both of their female crew members imposed their own will on them. So that always made Yamato a wild card viable option. But not reliable one. Their dream was never established, only implied and whatever backstory aka flashback that was supposed to develop her as a character had more lore implications for the Kozuki Clan, Kaido and to a lesser extent, Zoro.
How it concerns strength, Loki has yet to do anything that has implied he can out perform, Zoro, Sanji, even Jinbe and Especially Luffy. So what people are really saying is the Bounty discrepancies, but again, I feel a lot of the arguments here aren't being made in good faith. We all know that we've yet to see the fallout from the egghead incident. The Strawhats will be accused of collusion with Vegapunk and possibly be even painted as his killer.
We're in the middle of a full blown flashback centered on Elbaf and Loki is front and center, and he has some traumas boy let me tell you. Harald and Harujidin feel like the Tom and Iceburg in their roles of the flashback, I mean it's all right there. That can't be denied.
The only real concept things for Loki are his size. But two plot development introduced by Oda seemed meticulously added to address this. Franky learning more about Adam Wood on an island also known for Shipbuilding and whatever fruit Loki may or may not have.
If there is a dream to be revealed it is going to be likely revealed through Loki's meeting with Rocks or dialogue with Harald before his assassination.